1. Field of the Invention
The present invention relates to a flow control device and a flow control valve included in the flow control device used for a variety of devices that suitably control a flow rate of a fluid to supply the fluid, such as a flow control unit or the like in a semiconductor manufacturing apparatus.
2. Description of the Related Art
A known flow control valve is a diaphragm valve disclosed in Japanese Patent Laid-Open No. 2003-185053. The diaphragm valve in Japanese Patent Laid-Open No. 2003-185053 has a structure in which two upper and lower diaphragms 50 and 51 are connected by a link rod 52, and a piston 53 is connected to the upper diaphragm 50. When the piston 53 is moved upward by pressure of air from air supply piping 54, the movement of the piston 53 causes the upper diaphragm 50 to be deformed and separated from a valve seat 55 to open a channel 56 through which a fluid flows.
The diaphragm valve in Japanese Patent Laid-Open No. 2003-185053, however, has the structure in which the pressure of the air from the air supply piping 54 is applied to the piston 53 to deform the upper diaphragm 50, and thus an amount of change in the pressure when the pressure of the air is changed is directly reflected in an amount of deformation of the upper diaphragm 50 and an amount of separation from the valve seat 55, thereby making it difficult to finely adjust the amount of separation of the upper diaphragm 50 from the valve seat to hinder a flow adjustment with high accuracy. Because the diaphragm valve itself has low flow adjustment accuracy, flow control of a fluid with high accuracy cannot be expected in a flow control device using such a diaphragm valve.
Another known flow control valve is a pilot regulator used in a pure water flow control device disclosed in Japanese Patent Laid-Open No. 11-161342. The pilot regulator has a structure in which a valve body is connected to a diaphragm, and when operating pressure causes the diaphragm to be vertically displaced, the valve body vertically moves integrally with the diaphragm. Thus, in the pilot regulator, an amount of change in the operating pressure for vertically displacing the diaphragm is directly reflected in an amount of displacement of the diaphragm and an amount of vertical movement of the valve body, thereby hindering a flow adjustment with high accuracy like the flow control valve in Japanese Patent Laid-Open No. 2003-185053. Because the pilot regulator itself has low flow adjustment accuracy, flow control of a fluid with high accuracy cannot be expected in a flow control device using such a pilot regulator.